Forgot to say - if you get offered a place from a school on your CI list your original offer is automatically withdrawn. It is assumed that a school on your CI list is a higher preference to the school you already have. You cannot hold more than one offer at any given time. In my example - if you had accepted a place at DAO and then remained on the CI for HBS which was then offered, the DAO place would be automatically withdrawn - you would not get to choose between the two schools, you have already made that choice with your preferences.
Worth remembering - a lot of people rightly get used to the school they have been allocated, may have visited, bought uniform, met others going , tried out the route etc etc - then suddenly a place comes up elsewhere! hard enough if given the choice for some at that stage but worse if the choice is taken away from you.